The overall goal of this proposal is to examine how ultraviolent radiation (UVR) affects signal transduction pathways during fertilization, activation, and cell division UVR affects fertilization of sea urchin eggs, delays cells division in many cell types and affects Ca regulation and enzymes that control the cell cycle in mammalian cell lines. Therefore, effects of UVR on the initiation, amplitude and duration of Ca release at fertilization. Similarly, effects of UVR on the pH rise will be monitored using microinjection of BCECF dextran into unfertilized eggs followed by fertilization. Effects of UVR on the localization and enzymatic activities of PKC, PLCgamma, p58 Src-type kinase, and MAP kinase, all of which are activated, early, will be assayed by immunoblotting and immune complex enzymatic assays. In addition, pronuclear migration and nuclear envelope breakdown will be assessed using microscopy techniques. Finally, I will examine effects of UVR on activity of cyclins, cyclin targets of UVR on cell division in these eggs. I will examine whether they are protected by mycosporine-like amino acids that decrease UV-induced cleavage delays in sea urchins. These studies are significant because they will provide understanding of the basic molecular mechanism of signal transduction during fertilization and cell division and how UVR affects these processes.